Solvent extraction-spectrophotometric determination of aliphatic amines with metanil yellow

The solvent extraction-spectrophotometric determination of aliphatic amines was developed using metanil yellow (MY) as an ion associating reagent. Dihexylammonium ion (DHAH⁺), trihexylammonium ion (THAH⁺) and monododecylammonium ion (MDAH⁺) form stable ion associates with metanil yellow ion extracted into chloroform. These ion associates give absorption maximums at a wavelength of 402-407 nm. The absorbance is little influenced by inorganic divalent cations other than Ba²⁺ ions. The molar absorptivities of these ion associates were as high as 2.48 × 10⁴ - 2.62 × 10⁴ 1 mol^-1 cm^-1. It is considered that capillary condensation of neutral molecules between the contact points of the particles takes place in alkaline media in addition to normal adsorption of ionic and molecular species. This effect becomes large with decrease of particle size.